Centrifugal fan, and fan equipped with sound-muffling box and using centrifugal fan

ABSTRACT

Centrifugal fan includes casing and impeller, and discharge duct is connected to casing. At least one of tongue-part-side wall surface on tongue part side extending from casing outlet of casing and opposite tongue-part-side wall surface on side opposite to tongue part side extending from casing outlet protrudes into the inside of discharge duct, and outlet gas flow is bent at predetermined angle and is formed into discharge duct internal gas flow.

TECHNICAL FIELD

The present invention relates to a centrifugal fan, and a fan equippedwith a sound-muffling box and using the centrifugal fan.

BACKGROUND ART

At a casing outlet of a centrifugal fan with a scroll casing, velocityof gas blown out from an outer peripheral side (oppositetongue-part-side) of a casing is high. Further, a gas flow blown outfrom the casing outlet is liable to be bent in a rotational direction ofan impeller. Accordingly, in the centrifugal fan with a scroll casing, apressure loss is generated due to bending of a gas flow toward andischarge duct from the casing outlet. For the reduction of such apressure loss, in a conventional centrifugal fan the blowout directionof a gas flow at an outer peripheral portion of the casing where gasvelocity is high is directed toward an area in the vicinity of a centerportion of the discharge duct.

Hereinafter, the conventional centrifugal fan is described withreference to FIG. 10A and FIG. 10B. FIG. 10A is a side view of thecentrifugal fan described in PTL 1, and FIG. 10B is a side view of aconventional centrifugal fan of a general type.

As shown in FIG. 10A, centrifugal fan 101 a is constituted of casing 106a; and impeller 109 incorporated in casing 106 a. Casing 106 a is formedof side plate 104 provided with suction port 103, and scroll 105.Discharge duct 107 a is provided at outlet 102 a of casing 106 a.Suction duct 108 is provided at suction port 103. When impeller 109 isrotated, a gas which passes through suction duct 108 flows into casing106 a from suction port 103 by way of impeller 109. Then, pressure ofthe gas is boosted in casing 106 a, and the gas is blown out todischarge duct 107 a from outlet 102 a.

As shown in FIG. 10A, in centrifugal fan 101 a, the gas supply direction(discharge duct internal gas flow 111 a) of discharge duct 107 a isparallel to a plane orthogonal to a rotation axis of impeller 109. A gasflow blown out from outlet 102 a (outlet gas flow 110 a) is bent towardan opposite tongue-part-side in an area in the vicinity of tongue part112 by discharge duct 107 a so that outlet gas flow 110 a is formed intodischarge duct internal gas flow 111 a.

That is, a gas flow blown out from the opposite tongue-part-side ofcasing 106 a does not flow along a wall surface of discharge duct 107 a.The blowout direction of the gas flow is directed to a center portionbetween an upper side and a lower side of discharge duct 107 a in FIG.10A.

FIG. 10B shows a connection mode between centrifugal fan 101 b ofgeneral type and discharge duct 107 b. In FIG. 10B, symbols equal tosymbols used in FIG. 10A indicate identical constitutional elements. Asshown in FIG. 10B, a terminal end of casing 106 b and discharge duct 107b are substantially horizontal. In such centrifugal fan 101 b of ageneral type, discharge duct 107 b is fixed such that the direction ofoutlet gas flow 110 b at outlet 102 b and the direction of dischargeduct internal gas flow 111 b are directed in the same direction. Inother words, outlet gas flow 110 b blown out from casing 106 b advancesinto discharge duct 107 b by keeping the straight linear movement.

On the other hand, velocity of outlet gas flow 110 b is high at an outerperipheral side of casing 106 b. Accordingly, in the inside of dischargeduct 107 b, gas velocity at an upper side is higher than gas velocity atthe center portion between the upper side and a lower side of dischargeduct 107 b. As a result, when discharge duct 107 b is bent in the samedirection as rotational direction 114 at a downstream portion thereof, agas flow having a high gas velocity passes at an outer peripheral sideof a bent portion, and the gas flow smoothly flows along bending ofdischarge duct 107 b. On the other hand, when discharge duct 107 b isbent in the direction opposite to rotational direction 114 at thedownstream portion thereof, a gas flow having high gas velocity passesan inner side of the bent portion and hence, the turbulence of gas flowis generated at the bent portion of discharge duct 107 b. Thus, apressure loss is increased.

In PTL 1, casing 106 a is rotated in rotational direction 114 ofimpeller 109. Accordingly, in outlet gas flow 110 a, outlet gas flow 110a having high gas velocity at an outer peripheral side of casing 106 aflows into an area in the vicinity of a center portion between the upperside and the lower side of discharge duct 107 a. Then, in the area inthe vicinity of the center of discharge duct 107 a, outlet gas flow 110a spreads over the whole discharge duct 107 a, and flows in dischargeduct 107 a.

Outlet gas flow 110 a having high velocity is collected to the centerportion of discharge duct 107 a and hence, whichever direction dischargeduct 107 a is bent, a pressure loss generated by bending discharge duct107 a is reduced. Accordingly, it is possible to provide centrifugal fan101 a having a small pressure loss irrelevant to the bending directionof discharge duct 107 a.

However, when discharge duct 107 a is bent in the direction opposite tothe rotational direction of impeller 109 on a downstream side ofdischarge duct 107 a, it is necessary to increase a distance between thebent portion and the outlet 102 a.

CITATION LIST Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. 11-294393

SUMMARY OF THE INVENTION

In such a conventional centrifugal fan, a gas flow having high velocitycan be collected to the center portion between the upper side and thelower side of discharge duct 107 a shown in FIG. 10A. However, scroll105 is formed into a shape where hatched portion 116 in the vicinity ofoutlet 102 a is cut away, that is scroll 105 is formed into a shapewhere scroll 105 terminates half way. In scroll gas passage enlargingportion from an area in the vicinity of tongue part 112 of scroll 105 tooutlet 102 a, a velocity of a gas whose pressure is boosted by impeller109 is lowered due to the enlargement of scroll gas passage. That is,the scroll gas passage enlarging portion is a portion which converts agas into a static pressure from a dynamic pressure and makes the gasflow out into the inside of discharge duct 107 a. However, incentrifugal fan 101 a described in PTL 1, the scroll gas passageenlarging portion is short and hence, a velocity of the gas cannot besufficiently dropped in the scroll gas passage enlarging portion.Accordingly, the centrifugal fan 101 a described in PTL 1 has a drawbackthat performance (static pressure) of the centrifugal fan is lowered.

The centrifugal fan of the present invention includes: a casing having ascroll; and an impeller disposed inside the casing. The casing includesa side plate having a suction port. The scroll includes an outlet. Andischarge duct is connected to the casing. An outlet gas flow blown outfrom the outlet is parallel to a plane orthogonal to a rotational axisof the impeller. At least one of a tongue-part-side wall surface on atongue-part-side extending from a casing outlet of the casing and anopposite tongue-part-side wall surface on a side opposite to thetongue-part-side extending from the casing outlet protrudes into theinside of the discharge duct. As viewed from the direction orthogonal tothe suction port, the outlet gas flow is bent toward the side oppositeto the tongue-part-side from the tongue-part-side at a predeterminedangle and the outlet gas flow is formed into an discharge duct internalgas flow.

The scroll gas passage enlarging portion is increased by thetongue-part-side wall surface, the opposite tongue-part-side wallsurface or both the tongue-part-side wall surface and the oppositetongue-part-side wall surface and hence, a velocity of an outlet gasflow is sufficiently dropped so that the outlet gas flow is smoothlyintroduced into the discharge duct. Accordingly, in the outlet gas flow,the conversion into a static pressure from a dynamic pressure can besufficiently performed and hence, a pressure loss is prevented wherebylowering of performance of the centrifugal fan can be prevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a centrifugal fan according to a firstexemplary embodiment of the present invention.

FIG. 2 is a graph comparing performance of the centrifugal fan of thepresent invention and performance of a conventional centrifugal fan.

FIG. 3A is a side view of a centrifugal fan according to a secondexemplary embodiment of the present invention.

FIG. 3B is a front view of the centrifugal fan.

FIG. 4 is a side view of the centrifugal fan where a sound absorbingmember is disposed inside an discharge adapter.

FIG. 5 is a perspective view of a casing when small holes are formed ina tongue-part-side wall surface and an opposite tongue-part-side wallsurface of the centrifugal fan.

FIG. 6 is a side view for describing the duct connection of thecentrifugal fan.

FIG. 7 is a side view of a fan equipped with a sound-muffling box whichuses a centrifugal fan according to a third exemplary embodiment of thepresent invention.

FIG. 8 is a top plan view of the fan equipped with a sound-muffling boxwhich uses the centrifugal fan.

FIG. 9 is an installation view of the fan equipped with a sound-mufflingbox.

FIG. 10A is a side view of a centrifugal fan described in PTL 1.

FIG. 10B is a side view of a conventional centrifugal fan of a generaltype.

DESCRIPTION OF EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention aredescribed with reference to drawings.

First Exemplary Embodiment

FIG. 1 is a side view of a centrifugal fan according to the firstexemplary embodiment of the present invention. As shown in FIG.1,centrifugal fan 1 is constituted of casing 6; and impeller 9incorporated in casing 6. Casing 6 is formed of side plate 4 havingsuction port 3, and scroll 5 having outlet 2. Discharge duct 7 isconnected to casing outlet 6 a of casing 6, and suction duct 8 isconnected to suction port 3.

Opposite tongue-part-side wall surface 14 of scroll 5 on an oppositetongue part 13 b side and tongue-part-side wall surface 15 of scroll 5on a tongue part 13 a side protrude into the inside of discharge duct 7.Opposite tongue-part-side wall surface 14 does not reach the center ofdischarge duct 7, and an end portion of opposite tongue-part-side wallsurface 14 is disposed at a position in an upper half of discharge duct7 in FIG. 1. Open end of tongue-part-side wall surface 15 a oftongue-part-side wall surface 15 is in contact with discharge duct wallsurface 7 a. Opposite tongue-part-side wall surface 14 andtongue-part-side wall surface 15 extend from casing outlet 6 a.

Discharge duct 7 is connected to outlet 2 such that outlet gas flow 10which flows in outlet 2 is bent parallel to a plane orthogonal torotation axis 24 of impeller 9 and toward an opposite tongue part 13 bside on a side opposite to tongue part 13 a of scroll 5. That is, asviewed from the direction orthogonal to suction port 3, outlet gas flow10 is bent at a predetermined angle θ′ toward the opposite tongue part13 b side from a tongue part 13 a side, and forms discharge ductinternal gas flow 11 which flows in discharge duct 7. Predeterminedangle θ′ is larger than 0 degree and smaller than 45 degrees, andpreferably more than or equal to 20 degrees and less than or equal to 30degrees.

Since θ is expressed as θ=180−θ′ in FIG. 1, angle θ is a value exceeding135 degrees and less than 180 degrees, and preferably more than or equalto 150 degrees and less than or equal to 160 degrees.

Discharge duct internal gas flow 11 is also parallel to a planeorthogonal to rotation axis 24 of impeller 9.

Tongue part opposedly facing position 13 c is a position where aperpendicular extending downwardly to opposite tongue-part-side wallsurface 14 from tongue part 13 a intersects with oppositetongue-part-side wall surface 14. Connection portion 26 on an oppositetongue part 13 b side between casing 6 and discharge duct 7 is providedcloser to impeller 9 side than to tongue part opposedly facing position13 c.

The manner of operation and advantageous effects brought about by theabove-mentioned constitution of centrifugal fan 1 are described. Whenimpeller 9 is rotated, a gas which passes through suction duct 8 flowsinto the inside of casing 6 from suction port 3 by way of impeller 9,and a pressure of the gas is boosted inside casing 6, and the gas flowsout into discharge duct 7 from outlet 2.

Here, the most characterizing part of the first exemplary embodiment isdescribed. In the first exemplary embodiment, opposite tongue-part-sidewall surface 14 and tongue-part-side wall surface 15 are formed insidedischarge duct 7 such that scroll 5 protrudes into the inside ofdischarge duct 7, thus ensuring scroll gas passage enlarging portion 16.Accordingly, a gas which reaches casing outlet 6 a lowers a velocitythereof sufficiently in scroll gas passage enlarging potion 16 andhence, the conversion into a static pressure from a dynamic pressure isaccelerated, and the gas flows out into discharge duct 7.

Further, due to the formation of tongue-part-side wall surface 15,outlet gas flow 10 which impinges on tongue part 13 a is guided to theinside of discharge duct 7 along tongue-part-side wall surface 15. Sinceoutlet gas flow 10 is smoothly guided into discharge duct 7 bytongue-part-side wall surface 15 in this manner, a pressure loss causedby the sudden enlargement of the gas passage from tongue part 13 a todischarge duct 7 can be prevented.

Accordingly, it is desirable that tongue-part-side wall surface 15protruding into the inside of discharge duct 7 is configured such thatopen end of tongue-part-side wall surface 15 a is brought into contactwith discharge duct wall surface 7 a. However, open end oftongue-part-side wall surface 15 a is not necessarily brought intocontact with discharge duct wall surface 7 a.

A velocity of outlet gas flow 10 is higher on an outer peripheral sideof casing 6, that is, on an opposite tongue part 13 b side. Outlet gasflow 10 on the opposite tongue part 13 b side is bent by oppositetongue-part-side wall surface 14 in the direction of discharge ductinternal gas flow 11 at a center portion of discharge duct 7. In thismanner, in centrifugal fan 1 of the first exemplary embodiment, thevelocity of outlet gas flow 10 at the center portion in the inside ofdischarge duct 7 becomes high. Accordingly, whichever directiondischarge duct 7 is bent at a bent portion thereof on a downstream side,the increase of a pressure loss can be suppressed. That is, comparedwith the case where outlet gas flow 10 flows straightly and formsdischarge duct internal gas flow 11, a distance from outlet 2 to thebent portion of discharge duct 7 in the first exemplary embodiment canbe made small.

Discharge duct 7 is connected to casing 6 such that discharge duct 7 isarranged closer to an impeller 9 side than tongue part facing position13 c is and hence, centrifugal fan 1 can be miniaturized.

Further, discharge duct 7 is connected to casing 6 such that a centralaxis of discharge duct 7 is arranged close to impeller 9 and hence,centrifugal fan 1 can be miniaturized.

From a viewpoint of miniaturizing centrifugal fan 1, it is desirablethat discharge duct 7 is connected to casing 6 such that the centralaxis of discharge duct 7 passes rotation axis 24 (or a position in thevicinity of rotation axis 24) of impeller 9.

FIG. 2 is a graph comparing performance of the centrifugal fan accordingto the first exemplary embodiment of the present invention andperformance of a conventional centrifugal fan. FIG. 2 is a graphcomparing an amount of gas blown out from the centrifugal fan of thefirst exemplary embodiment which is indicated by graph (c), an amount ofgas blown out from the centrifugal fan shown in FIG. 10A which isindicated by graph (b), and an amount of gas blown out from thecentrifugal fan shown in FIG. 10B which is indicated by graph (a). Anamount of gas is taken on an axis of abscissas, and a static pressure istaken on an axis of ordinates. Graph (a) indicates a case where anoutlet gas flow from the centrifugal fan shown in FIG. 10B flowsstraightly and forms an discharge duct internal gas flow. Graph (b)indicates a case where an outlet gas flow from the centrifugal fan shownin FIG. 10A is bent to an opposite tongue part side and forms andischarge duct internal gas flow. Graph (c) indicates a case whereopposite tongue-part-side wall surface 14 and tongue-part-side wallsurface 15 protrude into the inside of discharge duct 7 in centrifugalfan 1 of the first exemplary embodiment, and outlet gas flow 10 is bentto the opposite tongue part 13 b side and forms discharge duct internalgas flow 11.

Compared to the centrifugal fan shown in FIG. 10B, the centrifugal fanshown in FIG. 10A has a smaller scroll gas passage enlarging potion.Further, a gas passage leading to an discharge duct is suddenly enlargedat the tongue part in the centrifugal fan shown in FIG. 10A and hence, astatic pressure is lowered as a whole. On the other hand, it isconfirmed that centrifugal fan 1 according to the first exemplaryembodiment has the substantially same performance as the general-typecentrifugal fan shown in FIG. 10B.

As described above, according to the centrifugal fan 1 of firstexemplary embodiment of the present invention, whichever directiondischarge duct 7 is bent, the pressure loss caused by bending ofdischarge duct 7 can be reduced and, at the same time, casing 6 can beminiaturized while suppressing the lowering of performance (staticpressure). Further, it is unnecessary to prepare two kinds of parts thatis, a part for the rightward rotation and a part for the leftwardrotation in conformity with the bending direction of discharge duct 7with respect to the parts of centrifugal fan 1 such as casing 6.Accordingly, the lowering of the pressure loss can be suppressedirrespective of the bending direction of discharge duct 7.

In the first exemplary embodiment, both of opposite tongue-part-sidewall surface 14 on an opposite tongue part 13 b side andtongue-part-side wall surface 15 on a tongue part 13 a side protrudeinto the inside of discharge duct 7 in casing 6. However, it issufficient that either one of opposite tongue-part-side wall surface 14on the opposite tongue part 13 b side and tongue-part-side wall surface15 on tongue part 13 a side protrudes into the inside of discharge duct7. In this case, the first exemplary embodiment can acquire advantageouseffects brought about only either one of opposite tongue-part-side wallsurface 14 on the opposite tongue part 13 b side and tongue-part-sidewall surface 15 on tongue part 13 a side.

Second Exemplary Embodiment

In the second exemplary embodiment of the present invention,constitutional elements having the same constitution as thecorresponding constitutional elements of the first exemplary embodimentare given the same symbols, and the detailed description of theseconstitutional elements is omitted and only different parts aredescribed. FIG. 3A is a side view of a centrifugal fan according to thesecond exemplary embodiment of the present invention, and FIG. 3B is afront view of the centrifugal fan.

Centrifugal fan 1 shown in FIG. 3A and FIG. 3B is installed such thatdischarge adapter 17 having a circular shape covers an outer peripheryof casing outlet 6 a in connecting discharge duct 7 having a circularshape to casing outlet 6 a. Discharge duct 7 having a circular shape isconnected to discharge adapter 17. Opposite tongue-part-side wallsurface 14 and tongue-part-side wall surface 15 protrude into the insideof discharge adapter 17. In this exemplary embodiment, tongue-part-sidewall surface width 15 c has the same size as impeller width 9 a.Further, gaps 21 are formed between tongue-part-side wall surface sides15 b and both left and right sides of discharge adapter 17.

The manner of operation and advantageous effects brought about by theabove-mentioned constitution of centrifugal fan 1 are described.

With respect to ensuring of scroll gas passage enlarging potion 16, theprevention of the sudden enlargement of the gas passage from tongue part13 a to discharge duct 7, and blowing of outlet gas flow 10 having highvelocity at the outer peripheral portion of casing 6 into a centerportion between an upper side and a lower side of discharge duct 7, thesecond exemplary embodiment has the constitution exactly same as theconstitution explained in conjunction with the first exemplaryembodiment. Impeller outlet gas flow 22 which is directly blown out fromimpeller 9 and has high velocity is liable to be influenced by thesudden enlargement of the gas passage. However, tongue-part-side wallsurface width 15 c and impeller width 9 a have the same size and hence,impeller outlet gas flow 22 flows along tongue-part-side wall surface15. Accordingly, impeller outlet gas flow 22 is smoothly guided to theinside of discharge duct 7 through discharge adapter 17.

On the other hand, velocity of side-plate-side outlet gas flow 23 on aside plate 4 side of impeller 9 is low. That is, side-plate-side outletgas flow 23 is minimally influenced by a sudden enlarging portion of thegas passage formed in gap 21 portions so that side-plate-side outlet gasflow 23 flows into a lower side of discharge adapter 17 and is guided todischarge duct 7. In this manner, due to the formation of gaps 21,impeller outlet gas flow 22 having high velocity and side-plate-sideoutlet gas flow 23 having low velocity are smoothly guided into theinside of discharge duct 7 without colliding with each other and hence,the pressure loss of impeller outlet gas flow 22 and the pressure lossof side-plate-side outlet gas flow 23 can be prevented.

Discharge adapter 17 connects casing outlet 6 a having a quadrangularshape following a shape of the extension of scroll 5 and discharge duct7 having a circular shape. Discharge adapter 17 is configured such thatdischarge adapter 17 has a circular shape on a scroll 5 side, and acircular cross-sectional area of discharge adapter 17 is graduallydecreased toward an discharge duct 7 side. Outlet gas flow 10 flows intothe inside of casing 6 through impeller 9, pressure of outlet gas flow10 is boosted inside casing 6, and outlet gas flow 10 reaches casingoutlet 6 a. Outlet gas flow 10 is smoothly guided to discharge duct 7from casing outlet 6 a by discharge adapter 17. At the same time, outletgas flow 10 is directed to a center portion of discharge duct 7.Accordingly, a diameter of discharge duct 7 can be reduced. Dischargeduct 7 is installed by being inserted into discharge adapter 17. Aportion of casing 6 is inserted into discharge adapter 17 and hence,centrifugal fan 1 can be miniaturized.

In this manner, in centrifugal fan 1 according to the second exemplaryembodiment of the present invention, casing 6 can be miniaturized,discharge duct 7 can be also miniaturized, and the installationworkability can be also improved while suppressing the lowering ofperformance (static pressure).

In the second exemplary embodiment, tongue-part-side wall surface 15 hasa flat planar shape. However, tongue-part-side wall surface sides 15 bmay be raised toward the opposite tongue part 13 b side with respect tothe gas supply direction or may be bent in the direction toward thetongue part 13 a side.

FIG. 4 is a side view of the centrifugal fan according to the secondexemplary embodiment of the present invention where a sound absorbingmember is disposed inside an discharge adapter. In centrifugal fan 1shown in FIG. 4, sound absorbing member 19 is disposed between dischargeadapter inner surface 17 a and opposite tongue-part-side wall surface 14as well as between discharge adapter inner surface 17 a andtongue-part-side wall surface 15.

The manner of operation and advantageous effects of centrifugal fan 1shown in FIG. 4 are described. A gas flow whose pressure is boostedinside casing 6 is flown out into discharge duct 7 from casing outlet 6a. At this time, outlet gas flow 10 impinges on discharge adapter 17 sothat gas flow noises are generated. Such gas flow noises are absorbed bysound absorbing members 19 disposed between discharge adapter 17 andcasing outlet 6 a of scroll 5.

FIG. 5 is a perspective view of a casing when small holes are formed ina tongue-part-side wall surface and an opposite tongue-part-side wallsurface of the centrifugal fan according to the second exemplaryembodiment of the present invention. As shown in FIG. 5, a plurality ofsmall holes 20 are formed in opposite tongue-part-side wall surface 14and tongue-part-side wall surface 15.

By forming the plurality of small holes 20 in opposite tongue-part-sidewall surface 14 and tongue-part-side wall surface 15, an energy of gasflow noises passes through small holes 20 so that the energy propagatesto spaces A, B shown in FIG. 4 disposed between scroll 5 and dischargeadapter 17 or to sound absorbing members 19 whereby gas flow noises areabsorbed. As a result, a sound absorbing rate in the inside of dischargeadapter 17 is increased.

FIG. 6 is a side view for describing the duct connection of thecentrifugal fan according to the second exemplary embodiment of thepresent invention. As shown in FIG. 6, central axis 25 of an opening ofdischarge adapter 17 passes rotation axis 24 of impeller 9 whichconstitutes the center of suction port 3.

As a result, a height of discharge duct 7 and a height of suction duct 8can be set equal to each other. Accordingly, when discharge duct 7 andsuction duct 8 are fixed to a floor or ceiling using members, a lengthof the members can be unified.

In the second exemplary embodiment, gaps 21 are disposed betweentongue-part-side wall surface sides 15 b and discharge adapter 17.However, gaps 21 may be disposed between tongue-part-side wall surfacesides 15 b and discharge duct 7.

Third Exemplary Embodiment

In a third exemplary embodiment of the present invention, constitutionalelements having the same constitution as the correspondingconstitutional elements of the first and second exemplary embodimentsare given the same symbols, and the description of these constitutionalelements is omitted and only different parts are described. FIG. 7 is aside view of a fan equipped with a sound-muffling box which uses acentrifugal fan according to a third exemplary embodiment of the presentinvention. FIG. 8 is a top plan view of the fan equipped with asound-muffling box which uses the centrifugal fan.

The fan equipped with a sound-muffling box according to the thirdexemplary embodiment includes: either one of centrifugal fans 1described in the first and second exemplary embodiments; and box-shapedbody 50 which incorporates centrifugal fan 1 therein. As shown in FIG. 7and FIG. 8, body 50 is constituted of: outlet panel 53; suction panel56; and side panels 58. Body blowout port 51 and discharge adapter 52are provided to outlet panel 53. Body suction port 54 and suctionadapter 55 are provided to suction panel 56. Checkup panel 57 is fixedto side panel 58.

Casing outlet 6 a is connected to discharge duct 59 by connectingdischarge adapter 52 to discharge duct 59. Further, discharge adapter 52is disposed at the center of outlet panel 53, and suction adapter 55 isdisposed at the center of suction panel 56. Although oppositetongue-part-side wall surface 14 and tongue-part-side wall surface 15are disposed inside discharge adapter 52 in the third exemplaryembodiment, in the same manner as the first exemplary embodiment or thesecond exemplary embodiment, either one of opposite tongue-part-sidewall surface 14 and tongue-part-side wall surface 15 may be disposedinside discharge adapter 52.

Top panel 60, bottom panel 61 and side panels 58 are positioned betweenoutlet panel 53 and suction panel 56. Top panel 60 and bottom panel 61are panels of body 50 which cover a top surface and a bottom surface ofcentrifugal fan 1, respectively. Checkup panel 57 detachably fixed toside panel 58 faces side plate 4 of centrifugal fan 1. Accordingly,after removing checkup panel 57 from side panel 58, an operator whoenters from wall surface checkup opening 63 can observe impeller 9 andmotor 62 fixed to side plate 4 through checkup panel opening 64.

Body blowout port 51 is formed at the center of outlet panel 53, andoutlet panel 53 faces casing outlet 6 a of centrifugal fan 1. In thethird exemplary embodiment, outlet panel 53 and centrifugal fan 1 areconnected and fixed to each other in a state where outlet panel 53 andcentrifugal fan 1 are arranged close to each other. However, outletpanel 53 and centrifugal fan 1 may be connected and fixed to each otherby way of an intermediate member.

Body suction port gas flow 66 supplied through body suction port 54passes centrifugal fan 1 and flows out as body blowout port gas flow 67through discharge duct 59 connected to discharge adapter 52 and suctionduct 65 connected to suction adapter 55. Discharge adapter 52 isdisposed at the center of outlet panel 53 and suction adapter 55 isdisposed at the center of suction panel 56, and discharge adapter 52faces suction adapter 55. Accordingly, discharge duct 59 and suctionduct 65 are installed on the same central axis 68. By providing bodysuction port 54 at the center of suction panel 56, body suction port gasflow 66 from suction duct 65 smoothly flows into body suction port 54.For this reason, it is desirable that body suction port 54 be providedat the center of suction panel 56.

FIG. 9 is an installation view of the fan equipped with a sound-mufflingbox according to the third exemplary embodiment of the presentinvention. When centrifugal fan 1 shown in FIG. 9 is operated, air inroom 70 is sucked through wall surface suction port 71, and isdischarged to outdoors 73 from wall surface outlet 72 through suctionduct 65, body 50 and discharge duct 59.

Wall surface checkup opening 63 is provided in the vicinity of checkuppanel 57 so that centrifugal fan 1 can be checked up. Body 50 isdisposed in attic 74 and hence, the miniaturization of centrifugal fan 1leads to the miniaturization of body 50. Accordingly, even when attic 74is narrow, body 50 can be easily installed.

The manner of operation and advantageous effects brought about by thefan equipped with a sound-muffling box which uses centrifugal fan 1according to the third exemplary embodiment of the present invention aredescribed.

As shown in FIG. 7, discharge adapter 52 is provided at the center ofoutlet panel 53, and suction adapter 55 is provided at the center ofsuction panel 56. Accordingly, when body 50 is installed upside down,that is, a top surface of body 50 is disposed on a lower side and abottom surface of body 50 is disposed on an upper side, positions ofdischarge adapter 52 and suction adapter 55 relative to body 50 are notchanged so that installation workability is improved.

The upside-down installation of body 50 is effectively applicable to acase where the inside of attic 74 shown in FIG. 9 is narrow so that theposition of checkup panel 57 with respect to body 50 is set upside down,that is, a case where body 50 is installed with wall surface checkupopening 63 disposed upside down.

As shown in FIG. 7, body blowout port 51 is provided at the center ofoutlet panel 53. Accordingly, body blowout port gas flow 67 from bodyblowout port 51 is directed to discharge adapter 52 disposed at thecenter of outlet panel 53 so that body blowout port gas flow 67 issmoothly guided without collision. Thus, a pressure loss can besuppressed.

Further, a distance between outlet panel 53 and centrifugal fan 1 isminimized so that body 50 can be miniaturized. Accordingly, it isdesirable that outlet panel 53 be in contact with casing outlet 6 a ofcentrifugal fan 1. However, it is not always necessary to bring outletpanel 53 into contact with casing outlet 6 a.

In this manner, according to the fan equipped with a sound-muffling boxwhich uses centrifugal fan 1 according to the third exemplary embodimentof the present invention, the installation workability is improved andbody 50 is miniaturized while suppressing the lowering of theperformance (static pressure).

INDUSTRIAL APPLICABILITY

The present invention is applicable to a ventilation blower such as aduct fan and to a centrifugal fan used in an air conditioner or thelike. The present invention is also applicable to cooling ofinstallation equipment by using a gas flow from a body blowout portbesides the conveyance of air by a ventilation blower or the like.

REFERENCE MARKS IN THE DRAWINGS

1 centrifugal fan

2 outlet

3 suction port

4 side plate

5 scroll

6 casing

6 a casing outlet

7 discharge duct

7 a discharge duct wall surface

8 suction duct

9 impeller

9 a impeller width

10 outlet gas flow

11 discharge duct internal gas flow

13 a tongue part

13 b opposite tongue part

13 c tongue part facing position

14 opposite tongue-part-side wall surface

15 tongue-part-side wall surface

15 a open end of tongue-part-side wall surface

15 b tongue-part-side wall surface side

15 c tongue-part-side wall surface width

16 scroll gas passage enlarging potion

17, 52 discharge adapter

17 a discharge adapter inner surface

19 sound absorbing member

20 small hole

21 gap

22 impeller outlet gas flow

23 side-plate-side outlet gas flow

24 rotation axis

25 central axis

26 connection portion

50 body

51 body blowout port

53 outlet panel

54 body suction port

55 suction adapter

56 suction panel

57 checkup panel

58 side panel

59 discharge duct

60 top panel

61 bottom panel

62 motor

63 wall surface checkup opening

64 checkup panel opening

65 suction duct

66 body suction port gas flow

67 body blowout port gas flow

68 same central axis

70 room

71 wall surface suction port

72 wall surface outlet

73 outdoor

74 attic

1. A centrifugal fan comprising: a casing having a scroll; and animpeller disposed inside the casing, wherein the casing includes a sideplate having a suction port, the scroll includes an outlet; and thecasing is connected to an discharge duct, an outlet gas flow which flowsthrough the outlet is parallel to a plane orthogonal to a rotation axisof the impeller, at least one of a tongue-part-side wall surface on atongue part side and an opposite tongue-part-side wall surface onanother side opposite to the tongue part side extending from the casingoutlet of the casing protrudes into the discharge duct, and as viewedfrom a direction orthogonal to the suction port, the outlet gas flow isbent from the tongue part side toward the side opposite to the tonguepart side at a predetermined angle, and formed into an internal gas flowwhich flows through the discharge duct.
 2. The centrifugal fan accordingto claim 1, wherein the predetermined angle is larger than 0 degree andsmaller than 45 degrees.
 3. The centrifugal fan according to claim 1,wherein an open end of the tongue-part-side wall surface is in contactwith a wall surface of the discharge duct when the tongue-part-side wallsurface protrudes into the discharge duct.
 4. The centrifugal fanaccording to claim 1, wherein a gap is formed between a tongue-part-sidewall surface side and the discharge duct when the tongue-part-side wallsurface protrudes into the discharge duct.
 5. The centrifugal fanaccording to claim 4, wherein a width of the tongue-part-side wallsurface is equal to a width of the impeller.
 6. The centrifugal fanaccording to claim 1, wherein a connection portion on the side oppositeto the tongue part side between the casing and the discharge duct iscloser to the impeller than a tongue part facing position at which aperpendicular extending downwardly to the opposite tongue-part-side wallsurface from the tongue part intersects.
 7. The centrifugal fanaccording to claim 1 further comprising an discharge adapter whichcovers the casing outlet, wherein the discharge duct and the dischargeadapter are connected to each other, and the tongue-part-side wallsurface and the opposite tongue-part-side wall surface protrude into thedischarge adapter.
 8. The centrifugal fan according to the claim 7,wherein a sound absorbing member is interposed between an dischargeadapter inner surface and the tongue-part-side wall surface and betweenthe discharge adapter inner surface and the opposite tongue-part-sidewall surface.
 9. The centrifugal fan according to the claim 8, wherein aplurality of small holes are formed in the tongue-part-side wall surfaceand the opposite tongue-part-side wall surface.
 10. The centrifugal fanaccording to the claim 7, wherein a center axis of an opening of thedischarge adapter passes the rotation axis.
 11. A fan equipped with asound-muffling box, the fan comprising: the centrifugal fan described inclaim 1; and a body in which the centrifugal fan is incorporated,wherein the body includes: an outlet panel provided with a body blowoutport and an discharge adapter; a suction panel provided with a bodysuction port and a suction adapter; and a side panel to which a checkuppanel is fixed, the discharge adapter is connected to the discharge ductsuch that the casing outlet is in communication with the discharge duct,the discharge adapter is disposed at a center of the outlet panel, andthe suction adapter is disposed at a center of the suction panel. 12.The fan equipped with a sound-muffling box according to claim 11,wherein the body blowout port is disposed at the center of the outletpanel.
 13. The fan equipped with a sound-muffling box according to theclaim 11, wherein the outlet panel is in contact with the casing outlet.